1. Field of the Invention
The present invention relates to a rotary element or body rotatably provided between two seat backs of a split-type vehicle seat, such as a foldable center backrest rotatably interposed between the two seat backs, and a rotation adjustment mechanism for angular adjustment of the rotary body. In particular, the invention is directed to an arrangement for supporting such rotation adjustment mechanism and rotary body in the split-type seat.
2. Description of Prior Art
A split-type seat is widely used as a rear seat (e.g. a second seat or third seat) having a pair of independent seats combined together as one seat unit, wherein the two seats each comprises a seat back and a seat cushion (see FIG. 1), as opposed to a normal bench rear seat which only consists of one integral seat back and seat cushion unit. In this split-type of seat, a rotary element or body, such as a foldable center backrest, rotatable-type armrest, and the like, is pivoted between two seat backs in such a way to be rotatable forwardly and backwardly relative to the two seat cushions. Thus, such rotary body can be set in a horizontally extending position where it is in a generally parallel relation with the seat cushions and can be set in an upright position where it lies substantially flush with the seat backs.
For instance, as can be seen from FIG. 1 (not the prior art), there is known a splititype rear seat having a center backrest (at 12) rotatably provided between the two separate seat backs. In most cases, this center backrest is of a bilaterally supported type wherein its both lateral walls are rotatably supported by a pair of connecting elements, respectively. As typically disclosed from the Japanese Laid-Open Patent Publication No. 2000-177459, the bilaterally-supported-type center backrest has two centers of rotation at the respective two lateral walls thereof, with such an arrangement that a rotation adjustment mechanism is provided at one of the two rotation centers to permit angular adjustment of the center backrest relative thereto, while on the other hand, a rigid hinge bracket (i.e. a free hinge element without any rotation adjustment means) is provided at another of them to allow free rotation of the center backrest relative thereto. In that way, the center backrest per se is stably supported between the rotation adjustment mechanism and hinge bracket in the split-type vehicle seat, while permitting for its angular adjustment to attain a desired inclination angle for supporting the back of a passenger.
However, in the foregoing conventional arrangement, it is found that a large spacing is defined between the rotation adjustment mechanism and hinge bracket due to the fact that they are disposed on the two respective lateral walls of center backrest. This means, in a way, that a maximum distance is given between those two elements. Therefore, dynamically stated, a load applied to the center backrest is inevitably imparted as an intensive great load only to the rotation adjustment mechanism, which necessitates a reinforcement of the latter to withstand the intensive great load. In other words, it is necessary to compensate for the dynamical imbalance of load exertion between the hinge bracket and rotation adjustment mechanism so as to prevent undesired twisting or deformation of the center backrest. This reinforcement has been done, for example, by increasing the thickness of connecting parts of the rotation adjustment mechanism, adding a reinforcing bracket thereto, or providing various reinforcements to the frame of rotation adjustment mechanism.
Nevertheless, those reinforcements are found defective in increasing the weight of associated reinforced portions and reinforcement part, making the structure more intricate, and increasing the costs involved.
In view of the above-stated drawbacks, it is therefore a primary purpose of the present invention to provide an improved arrangement for supporting a rotation adjustment mechanism of a rotary body in a vehicle seat, which is light in weight with inexpensive costs while providing an optimal dynamical balance for supporting the rotary body and rotation adjustment mechanism.
To achieve such purpose, the arrangement for supporting a rotation adjustment mechanism of a rotary body in a vehicle seat, in accordance with the present invention, basically comprises:
a bracket fixed to the vehicle seat, which is so adapted that the rotation adjustment means is rotatably supported thereon;
the bracket being provided within the rotary body such as to be disposed substantially at a central vertical line of the rotary body;
a hinge means without any rotation adjustment means provided therewith, which is so adapted that the rotary body is hingedly, rotatably supported thereon; and
the hinge means being disposed at one of two symmetrical lateral sides of the rotary body in relation to the afore-said central vertical line.
Accordingly, the bracket is situated centrally of and within the rotary body to provide a maximum strength sufficient to directly receive a great load applied to either of front and rear surfaces of the rotary body, thereby avoiding exertion of the load on the hinge means and eliminating a dynamical imbalance between the rotation adjustment mechanism and the hinge means as found in the prior art. Therefore, it is possible to positively prevent any twisting deformation of the rotary body, and also, the bracket requires no reinforcement, contributing to reduction of weight and costs involved.
Additionally, the rotary body remains stably supported at its both lateral sides between the bracket and hinge means, just in the same way as the ordinary bilaterally-supported structure stated previously.
Preferably, the bracket may be generally of a plate-like structure having a substantially planar both side walls and so disposed as to orient such both planar side walls in a direction to the central vertical line of rotary body, thus extending in a direction orthogonal with a widthwise direction of the rotary body. Further, such plate-like bracket be fixedly connected with a seat cushion of the vehicle seat, Hence, the bracket is not only easily given a rigidity enough to receive most of the great load without any reinforcement thereto, but also effectively escapes and disperses most of the great load through its wide planar wall down to the vehicle floor.